Conventionally, there have been a pressure transmitter, a pressure measuring device, etc. used for a pipeline for highly corrosive gas, chemical solution or the like. Such pressure transmitter, pressure detecting device, etc. are provided with a pressure sensor module that contacts the highly corrosive gas, chemical solution or the like to detect its pressure (refer to, for example, Patent Document 1 and Patent Document 2).
In a pressure sensor module according to Patent Document 1, a pressure guide member made of PFA (PerFluoroAlkoxylalkane) is fitted on an opening side of a diaphragm pressure sensor. A pressure frame also made of PFA is welded to the pressure guide member, and a diaphragm is bonded onto an inner surface of the pressure frame. A pressure sensor is provided on an inner surface of the diaphragm to convert a displacement of the diaphragm, which is generated by the pressure of the gas, chemical solution or the like as a fluid to be measured, into a variation in resistance and output the variation as an electronic signal. Herein, the surface of the diaphragm is coated with PFA resin in order to be protected against corrosion caused by the highly corrosive gas, chemical solution or the like.
In a pressure sensor module according to Patent Document 2, a flexible film is provided on a lip of a cavity, and a pressure sensor is provided on the top of the flexible film. The flexible film is displaced due to the pressure of a fluid to be measured, and the displacement of the flexible film is detected by the pressure sensor, so that the pressure of the fluid to be measured is measured. The flexible film is made of, for example, Teflon (the registered trademark of E. I. Du Pont de Numours and Company). A pattern of grooves or channels is formed on the flexible film, and pinhole paths are left in the flexible film. Further, a relieving passage into a central region of the cavity is formed from the side of a surface of the flexible film opposite to a surface of pressure sensor.
[Patent Document 1] Japanese Patent No. 3410711 (Page 2, FIG. 1)
[Patent Document 2] Japanese Patent No. 3323513 (Page 6, FIGS. 4 to 15)